1. Field of the Invention
The present invention generally relates to spinal stabilization systems that include at least one polyaxial fastener. Embodiments of the invention relate to spinal stabilization systems that may be inserted into a patient during a minimally invasive surgical procedure. Embodiments of the invention relate to tools used during a minimally invasive surgical procedure. Embodiments of the invention relate to methods of forming implant system components, methods of forming stabilization systems and components, and methods for performing minimally invasive spinal stabilization procedures.
2. Description of Related Art
Bone may be subject to degeneration caused by trauma, disease, and/or aging. Degeneration may destabilize bone and affect surrounding structures. For example, destabilization of a spine may result in alteration of a natural spacing between adjacent vertebrae. Alteration of a natural spacing between adjacent vertebrae may subject nerves that pass between vertebral bodies to pressure. Pressure applied to the nerves may cause pain and/or nerve damage. Maintaining the natural spacing between vertebrae may reduce pressure applied to nerves that pass between vertebral bodies. A spinal stabilization procedure may be used to maintain the natural spacing between vertebrae and promote spinal stability.
Spinal stabilization may involve accessing a portion of the spine through soft tissue. Conventional stabilization systems may require a large incision and/or multiple incisions in the soft tissue to provide access to a portion of the spine to be stabilized Conventional procedures may result in trauma to the soft tissue, for example, due to muscle stripping.
Spinal stabilization systems for a lumbar region of the spine may be inserted during a spinal stabilization procedure using a posterior spinal approach. Conventional systems and methods for posterolateral spinal fusion may involve dissecting and retracting soft tissue proximate the surgical site. Dissection and retraction of soft tissue may cause trauma to the soft tissue, and extend recovery time. Minimally invasive procedures and systems may reduce recovery time as well as trauma to the soft tissue surrounding a stabilization site.
U.S. Pat. No. 6,530,929 to Justis et al. (hereinafter “Justis”), which is incorporated by reference as if fully disclosed herein, describes minimally invasive techniques and instruments for stabilizing a bony structure in an animal subject. Justis provides a method for using an instrument to connect at least two bone anchors with a connecting element. The instrument is secured to the anchors and manipulated to place the connecting element in a position more proximate the anchors.
A spinal stabilization system may be installed in a patient to stabilize a portion of a spine. A spinal stabilization system may be installed using a minimally invasive procedure. An instrumentation kit may provide instruments and spinal stabilization system components necessary for forming a spinal stabilization system in a patient.
A spinal stabilization system may be used to achieve rigid pedicle fixation while minimizing the amount of damage to surrounding tissue. In some embodiments, a spinal stabilization system may be used to provide stability to two or more vertebrae. A spinal stabilization system may include an elongated member, two or more bone fastener assemblies, and/or a closure member. The bone fastener assembly may include, but is not limited to, a bone fastener and a collar. A first portion of the bone fastener may couple to a portion of the spine during use. A first portion of a collar may couple to a second portion of the bone fastener. A second portion of the collar may couple to an elongated member during use. In some embodiments, an orientation of the bone fastener may be independent of the orientation of the collar for a bone fastener assembly. After the bone fastener is placed in a vertebral body, the collar coupled to the bone fastener may be positioned so that the elongated member can be positioned in the collar and in at least one other collar that is coupled to another vertebral body by a bone fastener.
In an embodiment, a bone fastener assembly may include a bone fastener, a ring, and a collar. The ring may be positioned in the collar, Removal of the ring from the collar may be inhibited. A bone fastener may be positioned in the ring through a lower opening in the ring and in the collar. Splines of the bone fastener may be aligned with seats in the ring. The splines may be forced into the seats to couple the ring to the bone fastener. Separation of the ring from the bone fastener may be inhibited after the bone fastener is forced into the seats. The ring may angulate within the collar (i.e., the bone fastener may move relative to the collar within a defined range of motion).
In an embodiment, a collar may include, but is not limited to, arms and a body. Arms and body of a collar may form a slot to receive an elongated member. When the elongated member is positioned in the collar, a portion of the elongated member may be coupled to a bead of a bone fastener of the bone fastener assembly.
Inner surfaces of the arms of a bone fastener assembly collar may include a modified thread. The modified thread may engage a complementary modified thread of a closure member. A closure member may secure an elongated member to a bone fastener assemble. In some embodiments, a range of motion of a collar relative to a bone fastener may be skewed from a conical range of motion relative to a longitudinal center axis of the collar. The skew may be used to accommodate lordotic alignment and/or pedicle angle shift in adjacent vertebrae.
Different instruments may be used to form a spinal stabilization system in a patient using a minimally invasive procedure. The instruments may include, but are not limited to, positioning needles, guide wires, sleeves, bone fastener driver, mallets, tissue wedges, tissue retractors, tissue dilators, bone awls, taps, and an elongated member length estimator. An instrumentation kit may include, but is not limited to, two or more detachable members (e.g., sleeves), a tissue wedge, an elongated member positioner, a counter torque wrench, an estimating tool, a seater, closure member driver, and/or combinations thereof.
Detachable members may be used during installation of one vertebral level stabilization systems at each of the two vertebrae to be stabilized. In an embodiment, a detachable member may be coupled to a collar of a bone fastener assembly. A detachable member may include channels to allow movable members to advance and/or retract relative to the detachable member. In certain embodiments, movable members may be positioned through other portions of a detachable member. Movable members may couple to a bone fastener assembly collar. The movable members may inhibit translational and/or rotational movement of the collar relative to the detachable member.
An estimating tool may be used prior to insertion of an elongated member into bone fastener assemblies to estimate a desired length of the elongated member. The estimating tool may include arms. The arms may be positioned down detachable members to rest on top of collars or bone fasteners of bone fastener assemblies that are coupled to vertebral bodies. The arms of the estimating tool may be expanded to contact inner surfaces of the detachable members. When the ends of the arms contact the inner surfaces of the detachable members at the bone fastener assemblies, the estimating tool may be withdrawn from the detachable members. The arms may compress during removal, but will spring back to the measured distance between the detachable members adjacent the collar. The distance between the arms may be measured using a scale to provide an estimate of the appropriate elongated member length. Some additional length may be added to the estimated value to account for contouring of the elongated member and/or to allow the elongated member to extend beyond an end of at least two collars.
A tissue wedge may be used to form a plane between a first vertebra and a second vertebra during a minimally invasive procedure. The plane may accept an elongated member. In an embodiment, a tissue wedge may include a handle portion and a blunted blade. In some embodiments, the blade may be a double-wedged blade. One edge of the blade may include a hooked portion. The hooked portion may include a cutting edge for severing fascia. The hooked portion may cut fascia positioned in the hooked portion when the tissue wedge is drawn upwards.
In some embodiments, an elongated member positioner may be used to guide an elongated member through detachable members and position the elongated member in collars proximate pedicles of vertebrae. In an embodiment, an elongated member positioner may include a body and a plunger. The body may include a passageway, a handle portion, and an engaging portion. The plunger may contact the elongated member in the engaging portion in some cases, pressure supplied to an elongated member with an elongated member positioner may not be sufficient to seat the elongated member in collars of bone fastener assemblies. When the elongated member positioner cannot place the elongated member in the collars, a seater may be used to place the elongated member in the collars. The seater may include a handle portion. A grooved portion of the seater may be used to push the elongated member downwards into the collars.
In an embodiment, a closure member driver may position a closure member in a collar coupled to a bone fastener. The closure member driver may include a handle, an elongated portion and a coupling portion.
In certain embodiments, a detachable member may be held with a counter torque wrench to inhibit injury to the patient as the tool portion of a secured closure member is sheared off. In some embodiments, a counter torque wrench may include a handle portion and a sleeve portion. A distal end of the sleeve portion may engage an elongated member.
In an embodiment, a method for inserting a stabilization system in a spine may involve determining one or more vertebrae of the spine to be targeted for stabilization, making an incision in the skin, inserting a spinal stabilization system, and closing the incision in the skin.
During some surgical procedures, images of a patient may be taken to assist in determining target locations for insertion of bone fastener assemblies in vertebrae to be stabilized. A marking or markings may be made on the patient to indicate the target locations. An incision may be made in the patient's skin between the target locations. In some embodiments, the incision may be enlarged after insertion of a first bone fastener assembly. The targeting needle may be inserted into a first pedicle. Imaging may be used to monitor orientation and depth of the targeting needle during insertion.
After insertion of the targeting needle, a guide wire may be inserted through a hollow shaft of the targeting needle into the first pedicle. The targeting needle may be removed from the patient. A first bone fastener assembly coupled to a first detachable member may be inserted into the first pedicle.
A plane may be created in soft tissue between the first bone fastener assembly and a second pedicle. The plane may be formed without severing muscle tissue. If needed, fascia may be cut to facilitate formation of the plane. After the plane is formed, the targeting needle may be inserted in the first detachable member. A distal end of the targeting needle may be wanded through the plane and placed at an entry point of the second pedicle. The targeting needle may be inserted into the second pedicle in a desired orientation and to a desired depth. A guide wire may be inserted through a hollow shaft of the targeting needle into the second pedicle. The targeting needle may be removed, and a second bone fastener assembly coupled to a second detachable member may be inserted into the second pedicle.
An elongated member may be guided down the detachable member. The elongated member may be seated in the collars. A position of the elongated member in the collars may be confirmed using fluoroscopic imaging. After confirming the position of the elongated member, a first closure member coupled to a driver may be advanced down the first detachable members. The first closure member may be coupled to the fist collar. A counter torque wrench may be coupled to the detachable member. A head of the first closure member may be sheared. When the head is sheared, enough force is applied to the elongated member by the closure member to inhibit movement of the elongated member relative to the bone fastener assembly. The driver may be removed from the first closure member after coupling the first closure member to the first collar. The sheared off bead may be removed from the driver.
The driver may be coupled to a second closure member. A second closure member coupled to the driver and a counter torque wrench may be used wile the head of the closure member is sheared off to form the spinal stabilization system. The detachable members may be removed from the collars. The incision in the skin may be closed.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.